After newly designed photomasks and photomask blanks for electronic parts are manufactured in design or R & D departments, they are often transferred as samples to users of the products or to facilities in which they are mass-produced.
As is well known, photomasks are very sensitive, so that if a single particle of dust becomes attached to and/or a single or slight scar becomes formed on the photomask or the blank, the initial-designed function of the photomask becomes impaired. As a result, it is necessary to pay careful attention to the handling of the photomasks. Should a single dust particle become attached to and/or a single or slight scar be formed on the blanks for the photomasks, the initial-designed function of the blank will not be attainable, depending on the degree of defects in the photomask blank.
In order to solve the problems inherent in the conventional technology, the photomasks and photomask blanks are ordinarily contained in a plastic container, the gap between the container body and lid being completely sealed by adhesive tape or the like in order to make the container air tight before being transferred. This approach to handling the photomasks and photomask blanks is typically employed in the handling of spectroscopes, color filters and the like.
Recently, airplanes have been used to transfer goods in order to shorten the transfer time. It is well-known that there is no temperature or pressure control within the cargo sections of airplanes as there is in the passenger compartment. In particular, in airplanes traveling at high altitude along international air routes, the cargo sections experience pressures as low as 0.5 atmospheres and temperatures of less than 30.degree. C. Sudden changes in the environmental conditions within the cargo sections result in expansions and contractions of the containers and the contents therein. Such expansions and contractions create stresses which frequently result in breakage of the goods.
Obviously, the photomasks and the blanks for photomasks cannot be used and must be disposed of when large sections thereof are broken. Even if the photomask or the blank becomes chipped, the tiny chip often adheres to the surface of the photomask or the blank, thereby requiring its disposal.
In order to solve the problem associated with transferring such products by airplane, couriers often pack the containers in their bags and carry them in the passenger compartment until they arrive at their destination. This is not an ideal solution owing to the high cost of fares for a person relative to cargo fees and the fact that a preferable shipping arrangement may be missed due to the unavailability of a courier. The container transfer method using the cargo section of an airplane is very convenient, however, because the cargo section can be used during any airplane flight. Consequently, there is a need for a suitable container which is able to contain goods and be transferred in the cargo section of an airplane. Preferably, such container can be used to transfer not only photomasks and photomask blanks, but also electroscopes and color filters, all without breakage.